1 files changed, 59 insertions, 9 deletions

diff --git a/vendor/golang.org/x/crypto/ssh/cipher.go b/vendor/golang.org/x/crypto/ssh/cipher.go
index 34d3917c4f..aed2b1f017 100644
--- a/vendor/golang.org/x/crypto/ssh/cipher.go
+++ b/vendor/golang.org/x/crypto/ssh/cipher.go
@@ -135,6 +135,7 @@ const prefixLen = 5
 type streamPacketCipher struct {
 	mac    hash.Hash
 	cipher cipher.Stream
+	etm    bool
 
 	// The following members are to avoid per-packet allocations.
 	prefix      [prefixLen]byte
@@ -150,7 +151,14 @@ func (s *streamPacketCipher) readPacket(seqNum uint32, r io.Reader) ([]byte, err
 		return nil, err
 	}
 
-	s.cipher.XORKeyStream(s.prefix[:], s.prefix[:])
+	var encryptedPaddingLength [1]byte
+	if s.mac != nil && s.etm {
+		copy(encryptedPaddingLength[:], s.prefix[4:5])
+		s.cipher.XORKeyStream(s.prefix[4:5], s.prefix[4:5])
+	} else {
+		s.cipher.XORKeyStream(s.prefix[:], s.prefix[:])
+	}
+
 	length := binary.BigEndian.Uint32(s.prefix[0:4])
 	paddingLength := uint32(s.prefix[4])
 
@@ -159,7 +167,12 @@ func (s *streamPacketCipher) readPacket(seqNum uint32, r io.Reader) ([]byte, err
 		s.mac.Reset()
 		binary.BigEndian.PutUint32(s.seqNumBytes[:], seqNum)
 		s.mac.Write(s.seqNumBytes[:])
-		s.mac.Write(s.prefix[:])
+		if s.etm {
+			s.mac.Write(s.prefix[:4])
+			s.mac.Write(encryptedPaddingLength[:])
+		} else {
+			s.mac.Write(s.prefix[:])
+		}
 		macSize = uint32(s.mac.Size())
 	}
 
@@ -184,10 +197,17 @@ func (s *streamPacketCipher) readPacket(seqNum uint32, r io.Reader) ([]byte, err
 	}
 	mac := s.packetData[length-1:]
 	data := s.packetData[:length-1]
+
+	if s.mac != nil && s.etm {
+		s.mac.Write(data)
+	}
+
 	s.cipher.XORKeyStream(data, data)
 
 	if s.mac != nil {
-		s.mac.Write(data)
+		if !s.etm {
+			s.mac.Write(data)
+		}
 		s.macResult = s.mac.Sum(s.macResult[:0])
 		if subtle.ConstantTimeCompare(s.macResult, mac) != 1 {
 			return nil, errors.New("ssh: MAC failure")
@@ -203,7 +223,13 @@ func (s *streamPacketCipher) writePacket(seqNum uint32, w io.Writer, rand io.Rea
 		return errors.New("ssh: packet too large")
 	}
 
-	paddingLength := packetSizeMultiple - (prefixLen+len(packet))%packetSizeMultiple
+	aadlen := 0
+	if s.mac != nil && s.etm {
+		// packet length is not encrypted for EtM modes
+		aadlen = 4
+	}
+
+	paddingLength := packetSizeMultiple - (prefixLen+len(packet)-aadlen)%packetSizeMultiple
 	if paddingLength < 4 {
 		paddingLength += packetSizeMultiple
 	}
@@ -220,15 +246,37 @@ func (s *streamPacketCipher) writePacket(seqNum uint32, w io.Writer, rand io.Rea
 		s.mac.Reset()
 		binary.BigEndian.PutUint32(s.seqNumBytes[:], seqNum)
 		s.mac.Write(s.seqNumBytes[:])
+
+		if s.etm {
+			// For EtM algorithms, the packet length must stay unencrypted,
+			// but the following data (padding length) must be encrypted
+			s.cipher.XORKeyStream(s.prefix[4:5], s.prefix[4:5])
+		}
+
 		s.mac.Write(s.prefix[:])
-		s.mac.Write(packet)
-		s.mac.Write(padding)
+
+		if !s.etm {
+			// For non-EtM algorithms, the algorithm is applied on unencrypted data
+			s.mac.Write(packet)
+			s.mac.Write(padding)
+		}
+	}
+
+	if !(s.mac != nil && s.etm) {
+		// For EtM algorithms, the padding length has already been encrypted
+		// and the packet length must remain unencrypted
+		s.cipher.XORKeyStream(s.prefix[:], s.prefix[:])
 	}
 
-	s.cipher.XORKeyStream(s.prefix[:], s.prefix[:])
 	s.cipher.XORKeyStream(packet, packet)
 	s.cipher.XORKeyStream(padding, padding)
 
+	if s.mac != nil && s.etm {
+		// For EtM algorithms, packet and padding must be encrypted
+		s.mac.Write(packet)
+		s.mac.Write(padding)
+	}
+
 	if _, err := w.Write(s.prefix[:]); err != nil {
 		return err
 	}
@@ -256,7 +304,7 @@ type gcmCipher struct {
 	buf    []byte
 }
 
-func newGCMCipher(iv, key, macKey []byte) (packetCipher, error) {
+func newGCMCipher(iv, key []byte) (packetCipher, error) {
 	c, err := aes.NewCipher(key)
 	if err != nil {
 		return nil, err
@@ -344,7 +392,9 @@ func (c *gcmCipher) readPacket(seqNum uint32, r io.Reader) ([]byte, error) {
 	c.incIV()
 
 	padding := plain[0]
-	if padding < 4 || padding >= 20 {
+	if padding < 4 {
+		// padding is a byte, so it automatically satisfies
+		// the maximum size, which is 255.
 		return nil, fmt.Errorf("ssh: illegal padding %d", padding)
 	}